Method of producing motor fuels



9 May 26, 1959 E. R. CHRISTENSEN ET'AL 2,888,394

` METHOD OF PROOUOING MOTOR FUELS Filed vSep?l 14, 1955 United States Patent METHOD F PRODUCING MOTOR FUELS- Edward R. Christensen, Beacon, and Howard V. Hess, Glenham, N.Y;., assignors to The Texas Company, New York, N.Y., a corporation ofDelaware Application September 14, 1955, Serial No. 534,299

12 Claims. (Cl. 208-95) This invention relates to a process for treating petroleum fractions. More particularly, this invention rela'testo the treatment of naphthas for the manufacture of improved motor fuels or motor fuel components.

Petroleum fractions, such as light and heavy straightr L cyclization or aromatization of the parailins to aromatic j hydrocarbons.

do n ot always proceed equally Well under the same con'- Because these basic upgrading reactions ditions, single step treating processes employing these basic upgrading reactions have the disadvantageV that they are ineflicient with respect to the desired conversion t of A011e or moreof the components in the feedstock. On the other hand, multi-step treating4 processes have a disadvantage in that large volumes of feed material are handled in each step with the result that handling and` investment costs reduce the economies and' commercial. attractiveness of such schemes.

In accordance with our invention, We have providedl a combination treating process .wherein a peroleum, fraction is converted intoa high octanenmotor fuel corn-` ponent, and wherein only a portion, ofthe fraction is.v subjected to multiple treating steps.

A principal object of this invention is to providean im'- proved process for the treatmentof petroleum fractions. A further object is to provide a process for the manufacture of motor fuel components of improved quality. Still another Objectis to provide a combination treating process for a more etlicient conversion of petroleum fractions. will become evident from the accompanying detailed description and drawing which schematically illustrates a petroleum processing scheme of the practice of ourin-l vention.

Inraccordance with` this invention, there is provided a process for treating a petroleum fraction, such as a heavy straight run naphtha having a boiling` point in. the. range 175-450 F. `and containing straight chain and non-straight chain hydrocarbons, which comprises con.-vr verting saidV fraction, such as .by'catalytic reforming, e.g.

Platforming, to produce an effluent havingl improved,

How these and other objects are accomplished" motor fuel qualities, said effluent containing a substanry tianproportion of straight. chain and non-straightl chain hydrocarbons, fractionating `said efuent (reformate) to produce'l a relatively light fraction boiling` below about'k 250 F., e.g below about 210 F., and a remainingirelaf. tively heavy fraction, contacting said light fraction with a,solid adsorbent which selectively adsorbs straight chain hydrocarbons to the substantial exclusion of non-straight; chain, hydrocarbons to adsorb. straight chain khydrocar-l b9nsfrom,said,1ight fraction and blending' the resulting,...

Paieniea May ze, 1959 ice qualities; This product from the conversion of straightV chain` hydrocarbons may be'recovered separately, recycyled to the adsorption step to further remove straight chain hydrocarbons or it'may be blended with the aforementioned blend of said treated' light fraction and said heavy fraction.

A petroleuml fraction suitable for use in the practice' of this invention` might have an initial boilingpoint in the range 50-300or F. and an end point in the range 200-475 F., more or less. Furthermore, a petroleum fraction suitable for use in the practice of this invention must contain both straight chain and non-straight chain hydrocarbonsand might have the `following composition:

Naphthenes Aromatics. Paratins (including normal paratns and isoparatllns) Unsaturates (including normal olens and-isoolens) Thestraight chain hydrocarbons, for example the nor-iA mal. paraflincontent of petroleum fractions suitable for use in theL practice of'this invention, is frequently in the* range 3150% by volume. Typical reinery stocks which are applicable to the practice of this invention are a wide boilingstraight run naphtha, a light straight run naphtha,

a4 heavyV straightv run or a catalytic cracked naphtha, av

thermally cracked reformed naphtha. This invention,

however, is particularly applicable to the treatment of' catalytic reformates in the naphtha boiling range, such` as a'Platformate, a Hydroformate, an Ultraformate and the like.

Any-solidY adsorbent which selectively adsorbs straight chainf hydrocarbons to the substantial exclusion of nonstraigh't chain hydrocarbons canbe employed in the prac` ticeof-thisinvention. It is preferred, however, to employ:

as the adsorbent certainv natural orv synthetic zeolites'or alumino-silicates such as a calcium alumino-'silicate which exhibit the'properties of a molecular sieve, that is, adsorbentst made up of porous matter or crystals wherein the pores are ofmolecular dimension and are of uniformsize. A'particularly suitable solid vadsorbent for the adsorption of straight chain hydrocarbons tothe substan-v tialexclusion of-non-straight chain hydrocarbons is a` calciumi alumino-silicate manufactured by Linde Air Products- Company -and `designated Linde Type 5A Molecular Sieve.

cium alumino-silicate, `have a pore size or pore diameter ofabout 5 Angstrom units, a pore size eflcientto admit straight chain hydrocarbons such as the n-parains, to thesubstantial exclusion of the non-straight chain hydrocarbonsg. such.. as theiqnaphthenic, aromatic, iso-paraflinic, and' iso-oleinicf hydrocarbons.

. Other solid: selective adsorbents may be employed in the-practice of this invention. For example, it is contemplated-y that adsorbents having the property of selec-` tivelyadsorbing straight chain hydrocarbons to the substantialexclusionl of non-straight chain hydrocarbonsy in the manner o f a molecular sieve may be obtained by suitableitreatment, of. various oxide gels, especially metal. oxidegels ofthepolyvalentamphoteric metal oxides."

The crystals of this particular cal cium alumino-silicate, apparently actually a sodium cal` Other suitable selective adsorbents are known and include the synthetic and natural zeolites which, when dehydrated, may be described as crystalline zeolites having a rigid 3 dimensional anionic network having interstitial dimensions suiciently large to adsorb straight chain hydrocarbons but suiciently small to exclude the nonsented by the formula (Ca,Na) Al2Si4O12-2H2O andy which, after suitable conditioning, will adsorb straightl chain hydrocarbons to the substantial exclusion of nonstraight chain hydrocarbons. Naturally occurring or synl thetically prepared phacolite, gmelinite, harmotome and the like or suitable modifications of these products by base exchange are also applicable in the practice of this invention.

Other solid adsorbents which selectively adsorb straight chain hydrocarbons, such as n-paraflinsI and n-olefins, to the substantial exclusion of the non-straight chain hydrocarbons are known.

Referring now to the drawing which schematically represents one embodiment of the practice of this invention, a petroleum fraction in the Agasoline boiling range, such as a heavy straight run naphtha having an initial boiling point in the range l50-250 F. and an end point in the range 350-475 F. and containing straight chain and non-straight chain hydrocarbons, is introduced via line 11 into converter 12. Converter 12 may be a thermal.

or a catalytic converting unit, preferably a catalytic reforming unit such as a Platformer. The converting unit advantageously employs a platinum-containing reforming catalyst and is operated under reforming conditions to upgrade the petroleum fraction by dehydrogenation, isomerization and/ or dehydrocyclization. The resulting upgrading fraction is transferred via lines 13, 14 and 1S into fractionator 16. If, however, it is desired to remove the hydrogen and other lixed gases (methane and ethane) produced in the converting unit prior to introducing the resulting upgraded fraction into fractionator 16, the upgraded fraction is directed via line 13 into a liquid-gas separator 18. In the separator, the hydrogen and other fixed gases are removed overhead via line 19 and are available for recycle via lines 20 and 11 to supply hydrogen to the converting unit. In fractionator 16, the converted feed is separated into an overhead light fraction and a relatively heavy bottoms fraction. The light fraction boils below about 250 F., such as below 210 F.,l

and may amount to as much as 60% by volume of the converted feed from converter 12. The heavy fraction is separately recovered via line 23. It has been found that this relatively heavy fraction is more refractory or less responsive to upgrading, as evidenced by octane number increase, by a subsequent treating process (straight chain hydrocarbon adsorption separation). The light fraction is directed through line 22 to a heater 24. In heater Z4, the light fraction is brought up to a suitable temperature in preparation for the separatory adsorption operation for the removal of straight chain hydrocarbons,

therefrom. The heated light fraction is transferred via line 25 to adsorber 26.

In adsorber 26, the light fraction is contacted with a solid adsorbent, such as an alkaline earth metal aluminosilicate, preferably a calcium alumino-silicate, to effect the adsorptive separation of straight chain hydrocarbons therefrom. Adsorption conditions in the adsorber may range between about 300 to 750 F. and at any suitable pressure between -2000 p.s.i.\g. lt is preferred to maintain the adsorption conditions such that the light fraction undergoing treatment is in the vapor phase. After suitable contact within the adsorber to effect the adsorption of straight chain hydrocarbons, the treated light fraction,

4 7 now substantially free or at least having a reduced straight chain hydrocarbon content, is recovered via line 29. The resulting improvement in the treated light fraction as a motor fuel is evidenced by an increase in octane number. The thus-treated light fraction is blended via line 30 with the heavy fraction recovered via line 23 to produce an increased yield of high quality, relatively high-octane motor fuel.

On completion of the adsorption operation, the adsorber is subjected to desorption conditions to effect the removal of the adsorbed straight chain hydrocarbons. Suitable desorption conditions include a temperature in the range 500 F. to 1100" F. more or less, and a pressure in the range 0-1000 p.s.i.g. It is preferred to carry out the desorption operation under such conditions that the straight chain hydrocarbons are desorbed or recovered in the vapor phase. Desorption of the straight chain hydrocarbons is facilitated by the introduction of a stripping medium via line 32 to carry the desorbed straightV chain hydrocarbons from the adsorption zone.

Gases suitable as a stripping medum include hydrogen, nitro-s gen, carbon monoxide, carbon dioxide, methane, steam, iso-butane, as well as gases containing H2 and certain normally gaseous hydrocarbons such as methane, ethane and propane removed from the liquid-gas separator 18 via line 19.

The desorbed straight chain hydrocarbons and the ac-J companying stripping medium are conducted through line 33 into a liquid-gas separator 34. 1n the separator, thev stripping gases are separated and removed via line 3g for recycle to adsorber 26 or to converter 12, or the total desorption euent without separation may be directly passed to converter 36, particularly if the stripping gasv is comprised predominantly of hydrogen. The straight chain hydrocarbons remaining in separator 34 are transferred via line 35 to converter 36. Advantageously, the.

straight chain hydrocarbons are upgraded in converter 36 by isomerization. The resulting isomerized straight chain from the light fraction thereby producing an additionall upgraded fuel component.

If desired, the straight chain hydrocarbons, after desorpp tion, can be recycled directly to converter 12 to elect isomerization and dehydrocyclization. This operation is particularly advantageous when the hydrogen-containing j gas from separator 18 is employed as the shipping medium during desorption.

Illustrative of lthe practice of this invention, a heavy straight run naphtha having a boiling range in the range 175-475 F. is heated and passed to a catalytic reforming unit e.g., Platformer in contact with a platinum-containing catalyst under reforming conditions. Suitable reforming conditions include pressures in the range 150-900 p.s.i.g. and temperatures in the range 750l000 F., more or less. Platformer may have a boiling range of from F. to 440 F. and a research octane number clear of about 87. The reformate is conducted to a liquid-gas separator for the removal of hydrogen and fixed gases and the liquid from the separator heated and passed into a fractionator.

The fractionator is operated yto pass overhead a rela-f tively light fraction boiling below 250 F. and to leave behind a heavy bottoms fraction. The light fraction amounting up to about 60% by volume of the feed stream may have a research octane of about 8l While the heavy fraction may have a research octane number of about 98. The light fraction is contacted with a solid" The eluent or reformate from the.

adsorbent such as a sodium calcium alumino-silicam,E

eig. Linde'Type y5A Molecular Sieve, at fa temperature in the frange 425-650 F. to `effect adsorption, of the straight chain hydrocarbons therefrom. The resulting treated light fraction, now substantially free of straight chain hydrocarbons and having a research octane number substantially Iabout the vuntreated light fraction, is suitable for blending with the recovered heavy fraction to produce a motor fuel component having a substantially improved octane number.

It is not necessary to remove the straight chain hydrocarbons from the'aforementioned heavy bottoms fraction since this fraction already possesses la relatively --high octanev number and any octane improvement realized by removing the straight chain hydrocarbons therefrom would -be slight. This is indicated inthe accompanying Table No.1.v l

TABLE NO. I

Selective finishing of close boiling fractions from a Platformate [Whole Platformate 87.1 Clear Research Octane No.]

ASTM Res. Oct. Clear Boiling Vol. Per- Octane Out N o. Range, cent Treated for N o. Im-

F. Cumularemoval of provetive Unstraight ment treated chain hydrocarbons 1 10. 6 78. 9 89. 2 11. 3 2 20. 6 71. 0 82. 2 11. 2 3 30. 7 60. 6 73. 1 l2. 5 4 40. 7 78. 1 91. 0 12. 9 li 50. 7 82. 0 90.0 8.0 6 60. 8 86.6 94. 3 7. 7 7 249-254 70. 8 95. 6 99. 6 4. 0 8 2511-311 80. 9 97. 6 100. 9 3. 3 9 311-350 86. 1 101. 1 102. 3 1. 2 10 350-440 97. 9 103. 8 104. 6 0. 8

It will be seen that the response to octane improvement by the removal of straight chain hydrocarbons is best in the low boiling fraction amounting to 30 to 40 volume percent, i.e. the fractions boiling below about 210 F. The octane improvement of these fractions amount to about 12 octane numbers. 'Ihe fractions boiling between 210 F. and 250 F., show an improvement of about 8 octane numbers while the heavy portion of the fuel shows little response to the adsorption treatment. It is apparent from Table No. I that the adsorption of straight chain hydrocarbons from a reformate or Platformate is highly effective in upgrading a fraction boiling below about 250 F., amounting to about 60% of the whole reformate. In accordance with the practice of this invention, if a greater throughput is desired in the process, only those fractions showing maximum response to selective adsorption, i.e. the fractions boiling below about 210 F., should be treated in the adsorber. In this case, only about 40% of the reformate is subjected to adsorption thereby greatly increasing the throughput of the two stage process of this invention.

This application is a continuation-in-part of our application Serial No. 483,998, filed on January 25, 1955 which, in turn, is identified as a continuation-in-part of our copending application Serial No. 478,426, iled December 29, 1954.

As is evident to those skilled in the art, many modifications, substitutions and changes are possible in the practice of this invention without departing from the spirit or scope thereof.

We claim:

1. A process for treating a petroleum fraction containing straight chain and non-straight chain hydrocarbons which comprises catalytically reforming said fraction to produce an efduent suitable as a motor fuel component, said eiuent containing a substantial proportion of straight chain and non-straight chain hydrocarbons,

6 f'ractionatingk said f effluent ltofproducey alight fraction "boiling below'about 250 F. and a'heavy fraction, contacting said light fraction with va solid `adsorbent whichjselectively adsorbs straight chain hydrocarbons to the'substantial exclusion of non-straight chain hydrocarbons to adsorb straight chain hydrocarbons from -said fraction and blending the resulting treated light fraction and said heavy vfraction to vproduce a petroleum fraction having improved' qualities as amotor fuel.

2. A vprocess according to claim l'wherein-'the adsorbent is a calcium alumino-silicate.

3. A process according to claim l wherein the adsorbentis a sodium calcium alumino-silicate.

4. A process according to'claim 1 wherein-the adsorbent is an alkaline earth metal `alumino-silicate.

5. A process forthemanufacture of a motor fuelcomponent which comprises subjecting a hydrocarbon fraction in the naphtha boiling range to catalytic reforming to produce an eflluent having improved properties as a motor fuel component, said effluent containing straight chain and non-straight chain hydrocarbons, fractionating said eiuent to produce a light naphtha fraction boiling below about 250 F. and a heavy fraction, contacting said light fraction with a solid adsorbent which selectively adsorbs straight chain hydrocarbons to the substantial exclusion of non-straight chain hydrocarbons to adsorb straight chain hydrocarbons from said light fraction and blending the resulting treated light fraction and said heavy fraction.

6. A process for treating a petroleum fraction boiling in the range 75-450 F. which comprises catalytically reforming said fraction in the presence of a platinumcontaining catalyst to produce a reformate in the naphtha boiling range, said reformate containing straight chain and non-straight chain hydrocarbons, separating from said reformate a light fraction boiling below about 250 F. and a heavy fraction, contacting said light fraction with a solid adsorbent which selectively adsorbs straight chain hydrocarbons to the substantial exclusion of non-straight chain hydrocarbons to adsorb straight chain hydrocarbons from said light fraction and blending said light fraction, now substantially free of straight chain hydrocarbons with said heavy fraction.

7. A process according to claim 6 wherein the straight chain hydrocarbons are desorbed from the solid adsorbent and recycled to the catalytic reforming operation.

8. A process for treating a petroleum naphtha which comprises catalytically reforming said naphtha to produce an eiuent containing hydrogen and a reformate suitable as a motor fuel component,'said reformate containing straight chain and non-straight chain hydrocarbons, separating from said eiiiuent a hydrogen-rich gas and fractionating said reformate Iinto a light fraction and a heavy fraction, said light fraction boiling below about 210 F. and containing straight chain and nonstraight chain hydrocarbons, contacting said light fraction with a solid adsorbent which selectively adsorbs straight chain hydrocarbons to the substantial exclusion of non-straight chain hydrocarbons to adsorb straight chain hydrocarbons from said light fraction, desorbing said straight chain hydrocarbons from said adsorbent,

isomerizing said desorbed straight chain hydrocarbons hydrocarbons from said adsorbent and wherein the resulting desorbed straight chain hydrocarbons together with hydrogen-rich gas is passed to the isomerization operation.

12. A process for treating a petroleum naphtha which comprises catalytically reforming said naphtha to produce an efuent containing hydrogen and a reformate suitable as a motor fuel component, said reformate containing straight chain and non-straight chain hydrocarbons, separating from said eiuent a hydrogen-rich gas and fractionating said reformate into a light fraction and a heavy fraction, said light fraction boiling below about 210 F. and containing straight chain and non-straight chain hydrocarbons, contacting said light fraction with a solid adsorbent Which selectively adsorbs straight chain hydrocarbons to the substantial exclusion of non-straight chain hydrocarbons to adsorb straight chain hydrocarbons from said light fraction, desorbing said straight chain hydrocarbons from said adsorbent by contactingl said adsorbent with said hydrogen-rich gas, and passing ythe eiuent comprising desorbed straight chain hydrocarbons and said hydrogen-rich gas resulting from .the ldesorption operation to the aforesaid catalytic reformingoperation.

References Cited in the le of this patent I 

1. A PROCESS FOR TREATING A PETROLEUM FRACTION CONTAINING STRAIGHT CHAIN AND NON-STRAIGHT CHAIN HYDROCARBONS WHICH COMPRISES CATALYTICALLY REFROMING SAID FRACTION TO PRODUCE AN EFFLUENT SUITABLE AS A MOTOR FUEL COMPONENT, SAID EFFLUENT CONTAINING A SUBSTANTIAL PROPORTION OF STRAIGHT CHAIN AND NON-STRAIGHT CHAIN HYDROCARBONS, FRACTIONATING SAID EFFLUENT TO PRODUCE A LIGHT FRACTION BOILING BELOW ABOUT 250*F. AND A HEAVY FRACTION, CONTACTING SAID LIGHT FRACTION WITH A SOLID ADSORBENT WHICH SELECTIVELY ADSORBS STRAIGHT CHAIN HYDROCARBONS TO THE SUBSTANTIAL EXCLUSION OF NON-STRAIGHT CHAIN HYDROCARBONS TO ABSORB STRAIGHT CHAIN HYDROCARBONS FROM SAID FRACTION AND BLENDING THE RESULTING TREATED LIGHT FRACTION AND SAID HEAVY FRACTION TO PRODUCE A PETROLEUM FRACTION HAVING IMPROVED QUALITIES AS A MOTOR FUEL. 